1. Field of the Invention
Embodiments of the present invention generally relates to a thin film semiconductor device such as an organic light-emitting display device, and more particularly, to a thin film semiconductor device such as an organic light-emitting display which includes a thin film transistor (TFT) having improved electrical characteristics.
2. Description of the Related Art
Compared to a semiconductor device using a semiconductor substrate, when a thin film transistor (TFT) is formed by using a semiconductor thin film formed on a glass substrate, manufacturing costs may be reduced and a process for a large area may be easily performed, so that a thin film semiconductor device such as a flat panel display device is used in various fields.
An organic light-emitting display device is a self-emissive display apparatus that emits light and has characteristics of high brightness and a low operating voltage, so that the organic light-emitting display device has an excellent contrast ratio, can be formed as an ultra slim display apparatus, and is stable in realizing a moving picture at a response time of about several microseconds (μs). Also, the organic light-emitting display device does not have a limit in a viewing angle, is stable at low temperatures, and is driven with a low voltage of about 5 to 15 V (direct current (DC)), so that it is easy to manufacture and design a driving circuit for the organic light-emitting display device, and the manufacturing process is simple.
The organic light-emitting display device includes TFTs and a capacitor so as to control emission by pixels. For example, a TFT includes a semiconductor pattern formed of polysilicon. The semiconductor pattern includes a channel region and impurity regions that are doped with impurity at sides of the channel region. Since a doping density sharply changes at a boundary between the impurity region and the channel region, a strong electric field may be induced. The strong electric field causes a short channel effect or a hot electron effect, such that leakage current is increased and an off-current characteristic deteriorates.